(Not Applicable)
(Not Applicable)
The present invention relates in general to turbines and, more particularly, to seals for separating gas paths in a turbine.
The main gas-flow path in a gas turbine engine commonly includes a gas intake, a compressor, a combustor, a turbine, and a gas outlet. There are also secondary flows that are used to cool the various heated components of the engine. Mixing of these flows and gas leakage in general, from or into the gas path, is detrimental to engine performance and is generally undesirable.
One particular area in which a leakage path occurs is in the spacing between two gas turbine components such as adjacent vanes or ring segments. Sealing off this leakage path is problematic because the seal must be durable enough to last several thousand hours of operation and flexible enough to compensate for assembly misalignment, different engaging surfaces, vibration from operation, and unequal thermal expansion between adjacent components. Conventional seals, such as metal shims, are rigid and do not conform to the various misalignments; consequently, leakage occurs around the shims, which ultimately leads to a decrease in engine performance. Also, vibration and other relative movement of the adjacent components can wear the contact surfaces of the shim and introduce fracturing forces to the shim. Therefore, there is a need for an improved turbine gas-path leakage seal that can conform to various misalignments and that is easy to assemble and install.
Accordingly, it is an object of the invention to provide a seal for gas flow passages in a turbine that is constructed to provide a reliable seal in a vibrational environment.
It is another object of the invention to provide a turbine seal that is constructed to provide a reliable seal when sealed parts are misaligned due to manufacturing tolerances or operational displacement.
It is a further object of the invention to provide a turbine seal that is wear resistant under increased sealing pressure.
These and other objects of the invention are achieved by a turbine seal having a sealing shim having a top surface and a bottom surface, a first end portion, a second end portion, and a generally planar bridge portion connecting said first end portion and said second end portion. The first and second end portions extend downward at approximately 90 degrees from said bridge portion. At least one spring operatively contacts the bridge portion of said top surface of said sealing shim. The spring is biased against an opposing bearing surface of the sealed turbine parts, and urges the seal into forced contact with the sealing surfaces of the turbine parts. Thus, under operational dynamics, the sealing shim is urged to maintain a sealing contact.
Because this forced sealing contact can increase the wear on the shim, shim protection material is disposed generally between the first and second end portions and substantially adjacent to least a portion of the bridge portion on the opposite side from the spring. The shim protection material can be secured to the shim according to a variety of techniques of the invention. The shim protection material can include one or more layers of cloth made of metal fibers or the like. The alignment of fibers in each cloth are preferably angled relative to the longitudinal dimension of the shim.
The shim protection material can substantially abut the first and second end portions and be secured to the first and second end portions by seam welds. Alternatively, a pair of rails can extend downward from the bottom surface of the shim bridge portion. The shim protection material can extend between and substantially adjacent to said pair of rails and be secured to said pair of rails by seam welds.
The seal assembly according to the invention can also include a leaf spring having a curved cross-sectional profile. The profile defines a vertex portion extending to opposing base portions. The profile has a substantially flat region over at least half the cross sectional length and curving to the base portions.
The seal assembly can be used to seal various gas flow passages in a turbine environment, including, for example, adjacent turbine vanes, blades or turbine ring segments.